Power supply?


Old 01-04-06, 10:48 PM
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Power supply?

My desktop is about 4 years old.... ABout a week before the following concern, I had taken it to the shop to blow out all the dust bunnies (a yearly ritual).

It shut down normally one night but refuse to boot the next morning. Closer inspection shows the power LED on the mobo comes on when the master switch is turned on. When I push the switch on the front panel, the fans will turn a couple of times and then stop.... connecting a DMM to the yellow and black wires shows the voltage will start to rise when the fans are trying to spin up and will immediately drop to zero. Pushing the button a second or third time will not spin the fans or give a voltage rise. Turning the master switch off and then back on will allow this to repeat but only if the power LED is allowed to go out (it stays on for several seconds after the master switch is turned off).

I've unplugged all the disc drives with no change.

Is it safe to assume that the power supply is faulty or are there further diagnostics I need to perform?

Any help appreciated....
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Old 01-04-06, 11:38 PM
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I had the samething happen to me a few years ago and my power supply was toast. The only issue I had I found out later that my surge protect died and I caught a surge that not only burnt my power supply, but also burned my mother board as well. What kind of power supply is it? Do you have a processor fan on the heat sink? If not I woud recommend looking it getting, because your processor maybe getting over heated and shutting off, I have seen that happen more than I can count

Last edited by griffelkin2002; 01-05-06 at 12:43 AM.
Old 01-05-06, 12:37 AM
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Check the heat sink for your CPU...it may have came loose during dust bunny extraction. If so, the power may be shutting off to prevent burning up your processor...

If the heat sink is loose, remove it, clean off the goo from the old thermal paste on both the processor and heat sink (rubbing alcohol in moderation--think Q-tip), and get some good thermal paste to reapply--go easy on it...follow the directions that come with the paste.
Old 01-05-06, 03:08 PM
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Not all motherboards (especially older ones) have cpu thermal protection; there are a great many that are happy to cook your cpu into oblivion. That said, removing and reapplying the heatsink + fan combo is fairly straightforward and worth a shot, as chirkware mentioned.

If you don't have any thermal compound to reapply between the cpu and heatsink arctic silver makes some good stuff that is easy to use. Don't worry about which one to buy they'll all get the job done.

Do you have another PC around that you can steal the power supply from? If so, that's another somewhat quick test that can be done.
Old 01-06-06, 12:52 AM
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Naturally, none of the "donors" that I have use the same mobo connections as what I currently have. Being a fatalist, I'll spring for a 400 watt or better power supply and try it.... if nothing else, it will be a decent start on the next desktopper...

Thanks, folks, I'll let you in on all the gory details once I have a chance....
Old 01-06-06, 11:44 AM
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If it's an ATX board, you could also unplug all power connectors and jumper the main plug to see if the power supply will power up and stay on. Jumpering the green wire on the main plug to any black wire will do it. Insert the jumper wire (a paper clip will work) with the power supply unplugged for safety and make sure ALL other power connectors are removed.
Old 01-22-06, 11:45 AM
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Well, the PS didn't help at all... being at the envelope of my knowledge, it was off to the local shop.... mobo is frapped. It's never a good thing to hear that your not so old, state of the art mobo is impossible to find parts for...

Rather than purchase a new system, I decided a new mobo, 3 gig processor and new RAM (one gig) is about as good a choice as any.... he'll through in a "pretty" box for free.

Thanx for the help, folks....

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